UC Davis

The Evapotranspiration Rate (ETo) of a given geographic region directly regulates the decomposition rate of vertebrate carrion, with any deviation attributed to insect activity. We conducted four decomposition experiments using pig carrion (Sus scrofa) over the span of two years (2018-2020) at a location in Davis, California. We used ETo, a variable that accounts for five climatic parameters: wind, temperature, humidity, solar radiation, and altitude, as the rate-determining variable of the decomposition process. We found ETo to have a strong (R2 = 0.97) predictive relationship with the decomposition rate. To account for maggot activity actively decomposing the carrion, we measured maggot weight in 2019 and 2020 using a novel method, and in 2020 we used FLIR imagery to measure maggot mass temperatures as a surrogate measurement of total maggot activity. Maggot activity was shown as a significant predictor (p-value < 0.0001) of the decomposition rate, while maggot weight was not (p-value > 0.1). We hope to show the forensic entomology community the potential of using ETo. Future projects can incorporate ETo to decomposition studies to determine if ETo is the most accurate descriptor of decomposition and ultimately increase certainty in the Postmortem Interval (PMI).